Leaving out the skill/conscientiousness of the tyre fitter and the particular machine that the wheel was balanced on, is tyre balancing carried out to the same standard/accuracy regardless of the potential top speed of the vehicle?
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L\'escargot.
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Most cars seem to have a critical speed where you feel unbalanced wheels-probably something to do with spring rates-usually well below maximum-having said that,our local tyre fitting place offers std. wheel balancing which has never given me any concerns and,for a bit extra, "ultra-accurate" to 0.1g.
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Escargot, I think the answer is No, but I'd be interested in others' views.
What does bother me is that wheel balancing seems to be rather a lottery. In my experience, there's a high probability that the fitter gets it wrong and I have to go back and have them re-done - I'm talking fronts primarily. Yet I've never had the problem of poorly balanced wheels on a new car. Go figure...
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had the problem of poorly balanced wheels on a new car. Go figure...
Car manufacturers will undoubtedy have inspection procedures and tolerances for wheel balancing just as it does for every other feature on a car.
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L\'escargot.
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I drove around for 6 months with a vibration through the steering at 50-70mph. I had the wheels rebalanced twice by the place who fitted the tyres and eventually decided it was worn suspension components.
Last month, I had the wheels rebalanced for a third time at a tyre place which had a Hunter balancing machine.
The vibration has now gone.
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Won't there be a number of speeds at which resonance can occur? I was wondering how fast I'd have to drive to check that my front wheels are sufficiently in balance after having had new tyres fitted.
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L\'escargot.
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Correction ~ I was wondering what speed I'd have to get up to to check ...........
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L\'escargot.
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Most wheel balancing only balances the tyre to the wheel (obvious maybe).
For greater accuracy find somewhere that will use an on car wheel balancer to balance the (balanced) wheel and tyre to the car.
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There are two speeds which generally show up improper wheel balancing.
55-56mph and approx. 90mph. Obviously the second doesn't matter in everyday, UK, driving.
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>>There are two speeds which generally show up improper wheel balancing.
Yes - at least two.
The speeds depend on the car.
The first, lower, speed is where any static imbalance excites the wheel hop resonance. The wheel hop frequency at resonance depends on the unsprung mass, the effective stiffness of the tyre/road and the stiffness of the suspension.
The second, higher, speed is where any dynamic imbalance excites a steering system resonance. This resonant frequency depends on the rotational inertia of the swivel hub and wheel, and the effective stiffness of the steering linkages as experienced by the wheel/hub.
I have never needed to go to better accuracy than 5g masses at the wheel rim in order to get good balance.
The balancing machines are typically used very roughly, and I wouldn't be surprised to find that in many cases the transducers have been damaged by this rough handling, and are not producing a sufficiently accurate output signal. In a decent machine, there will be two transducers, and, in order to get good balance, the magnitude of the signal from each, and the phase of the signal relative to the wheel rotation from each must be accurate to enable both static and dynamic balance to be acheived.
Number_Cruncher
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I drove around for 6 months with a vibration through the steering at 50-70mph. I had the wheels rebalanced twice by the place who fitted the tyres and eventually decided it was worn suspension components.
Could they comment on why you didn't have the wobble before you got the new tyres ?
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Manufacturers get the "best" tyres to come off the production line - ie those without too many heavy and light spots in the build.
Hence new cars have less balance problems.
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I got some tyres fitted that were badly balanced and took 2 attempts to get them right. Due to being busy at work it took me about a month to get round to getting them done right, and in that time I noticed a slight reduction in fuel consumption, 2-3mpg on the dashboard display, that I could not attribute to anything else. So it pays in more ways than one not to drive round with wobbly wheels..
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Manufacturers get the "best" tyres to come off the production line - ie those without too many heavy and light spots in the build.
I used to work in a car factory and the whole tyre fitting process was automated - even 30 years ago. We used to reject a fair number - scores I would say, but bear in mind we were using maybe 5000 per day - of tyres that were out of the balance spec.
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I've had loads of wheel balancing troubles on my cars over the years, almost all down to sloppiness of the fitter using the machine.
IN the latest instance I had the wheels balanced twice by the place I bought the tyres from only to get fed up with this and pay a 'better' tyre place to balance them properly. I'd say the reasons are, worn out or damaged balancing machines or infrequent calibration of machines. In fact my findings are that you never get a good balance from the mobile van-based fitters as their machines get abused so much by being carted around in the vans. I understand that most car makers now use a 'road force balancer' on new cars which not only balances the wheels on the car but also balances the tyres with respect to varying road forces as the tyre revolves under compression. These machines do exist in the field but are very had to locate. The only one I have ever heard of is in the Bentley main-dealers in Pangbourne Berkshire.
However I re-itterate, that used carefully, the regular machines with daily calibration should do the job properly 99% of the time.
There is one other issue that springs to mind with Alloy wheels in that sometines with some alloys, it is difficult to put weights where they need to be if they should be on the very outer rim of the wheel, and on such occasions I think a compromise has to be reached with weight positioning.
I just wish tyre fitters would wake up and realise that we dont just use our cars for popping to Sainsburys on occasion, but DO use them for driving for hours on the continent at 85+ !!
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These machines do exist in the field but are very had to locate.
There's a centre locator here:
www.pro-align.co.uk/products/balancers/psgsp9700.h...m
but you'd need to check whether they have one of those ballancers. Perhaps Pro-Align will tell you if you ask them?
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I understand that most car makers now use a 'road force balancer' on new cars which not only balances the wheels on the car but also balances the tyres with respect to varying road forces as the tyre revolves under compression. These machines do exist in the field but are very had to locate. The only one I have ever heard of is in the Bentley main-dealers in Pangbourne Berkshire
Very few places do have the "on car" balancers, but most Volvo dealers will have 1. Also most "good" tyre places will have 1. especially competetion orientated outlets.
Any half decent tyre place should know somewhere local where there is 1.
In fairness to the national fastfit places, most of their employees have probably never heard of 1. But as always, find a good independant and they should be able to sort you or point 1 out for you. If your place doesnt know of 1, then how "good" are they would be my question?
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At one time there were spots on tyres to aid fitting, to get the best initial balance to minimise the amount of weights needed. I think the spot showed a heavy point and it was recommended that this point was opposite the valve. Does this still apply, and if so do tyre fitters adhere to the recommendation?
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L\'escargot.
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I had "on-car" balancing done in the late 1960s when I had a Hunter which suffered badly from vibration problems. I think it was a common problem connected with the Macpherson suspension design of that era. The original balance weights were removed and, with the front of the car jacked up, the wheels were, one at a time, run up to speed. The vibration was painful to watch ~ I thought the bonnet was going to fly off the car and the car was going to jump off the jack. Never again! Never, never, never!
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L\'escargot.
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Dynamic balancing is the best where the tyre is removed from the rim & the wheel checked fore balance 1st then the tyre checked on its own & the two heaviest spots fitted opposing one another & then all balanced as a mass. There are not many tyre places that do it but its worth having done if you have a car that sufferes from wheel balance problems.
Yep your quite right L'escargot that means if you get a slight tremor at 90 its gonna be very bad at 180. The sesetivity of the machine is gonna be the factor in balance at high speed
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had "on-car" balancing done in the late 1960s
It is a little different now !
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In the 1960s the car was raised at the front on a jack. The wheel was then spun up to speed by pressing a rotating roller up to the tyre. How is it "a little different now"? Please describe the procedure.
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L\'escargot.
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